This invention relates to double layer capacitors, and more particularly relates to high-energy, high-power electrolytic capacitors.
Conventional electrolytic capacitors store energy by accommodating a so-called double layer of charge at the interface of each capacitor electrode surface and the electrolytic solution between the electrodes. The electrode surface area thus limits the energy storage capacity of such capacitors; the larger the electrode surface area, the larger the double layer of charge which may be generated, and hence the greater the energy storage of the capacitor. Typical applications restrict the practical limit of a capacitor's physical size, however, and thereby limit the achievable energy storage capacity provided by the macroscopic surfaces of the capacitor.
One double layer capacitor design which overcomes the macroscopic capacitor surface area limitation employs powdered electrode materials, e.g., high-area, activated carbon particles, to microscopically increase the surface area of the capacitor electrodes. In such a capacitor, the carbon particles are bound together to form a porous electrode structure in which the exposed surfaces of the particles contribute to the overall electrode surface area. The internal resistance and capacitance of the porous electrode structure is a complicated function of the carbon particles' structure and configuration.